This invention relates to agricultural implements. In particular, this invention relates to the transport of a granular product, such as seed.
In many agricultural implements, a dry granular product, such as seed, fertilizer and the like, must be transported from a central containment unit to a number of secondary containment units. Commonly, pneumatic units are used to drive the seed through delivery lines from the central containment unit to the secondary containment units. These secondary containment units may be spread out over a large area to provide a large coverage area.
Transport of the seed from the central containment unit to the secondary containment units may occur as dilute phase transport or dense phase transport. In dilute phase transport, there is a large amount of air relative to the product being transported. In dense phase transport, there is a greater ratio of product to air volume in the delivery line.
Although dense phase transport is desirable for moving larger quantities of product, control of the flow of the product is difficult, particularly with respect to starting and stopping product flow. As dense phase transport requires substantially filling the delivery line with the granular product being transported, the operation of valves within the delivery line can be problematic. The operation of a valve may displace the seed being transported and/or may crush and damage the seed. Moreover, closed valves will result in the buildup of pressure in the delivery lines that will cause a sudden surge when the valve is opened. Although the flow of air could be turned on or off to start or stop the transport, this may add extra cost in the form of variable speed pneumatic units or the like. Moreover, the when there are a plurality of delivery lines, stopping the flow to one of the lines or a segment of the line may require complex pneumatic arrangements or multiple air sources.
Hence, a need exists for an improved system and method to control the dense phase transport of a granular product, such as seed, through a delivery line. In particular, there is a need to control the dense phase transport of seed without an inline valve that could damage the product or require complex control systems.